The Missouri Department of Transportation initiated a study of that segment of Route US 60 that has been officially designated as “emergency vehicle priority access”. The objectives were to establish a current subsurface and earthquake design geographic information systems (GIS) database for the designated US 60 corridor, and to conduct detailed earthquake assessments at two critical bridge sites along US 60. Databases have been established for current subsurface and earthquake data for the US Route 60 corridor in Butler, Stoddard and New Madrid Counties. These databases serve as the beginning of a larger regional or statewide database for future development and usage by MoDOT. Detailed earthquake site assessments have been conducted for two critical US 60 roadway bridge sites (Wahite Ditch and St. Francis River Bridge). Liquefaction potential, slope stability, abutment stability, and structure stability analysis were performed at both sites for selected “worst case scenario synthetic bedrock ground motions” based on New Madrid source zone earthquakes with 2% and 10% probabilities of exceedance in fifty years. Site assessments indicate that both the Wahite Ditch and St. Francis River bridges could be rendered unusable by strong ground motion with a 2% probability of exceedance in the next fifty years. Studies indicate that the bridge themselves would not fail - rather they would probably be rendered unusable because of damage to their abutments and the failure of their approaches (as a result of slope instability and liquefaction). Problems could be exacerbated by the localized flooding as a result of levee failure and/or damage to the Wappapello Dam. A scheme of retrofit of these structures will be developed later
